NEW YORK -- Two new musicals share this rather old-fashioned oddity, that their music is the most important thing about them. But one has little more to offer, while the other has a lot.

Unsurprisingly, the first is "Jersey Boys," the latest version of that current Broadway staple, the so-called "jukebox musical" -- a show whose raison d'etre is to showcase (exploit?) music by or associated with some pop star. Recent examples are "All Shook Up" (Elvis), "Good Vibrations" (the Beach Boys), "Lennon" (duh) and, going back a bit, the mother lode of such constructs, "Mamma Mia!" (ABBA).

With "Jersey Boys," the heart of the matter is in the subtitle, "The Story of Frankie Valli & The Four Seasons." Both its attractions (the music) and demerits (the story) are right there.

The other new show, "The Light in the Piazza," is not really new, since it debuted in time to garner Tony Awards last June. Here, the music by Adam Guettel is a real charm -- but the story, conflicts and something as difficult to capture as the atmosphere are all attractions in themselves.

'Jersey Boys'

More precisely, "Jersey Boys" is a hybrid, a jukebox musical in motivation but also the musical version of a bio-pic, a real-life story of the rise and fall, etc., of a singing group, a genre that pre-dates the more open exploitation of jukebox shows.

The members of the Four Seasons came out of the same suburban strip mall, Italian-American New Jersey culture that later gave us "The Sopranos," complete with godfather figures and an acquaintance with the Rahway Academy for the Arts, better known as prison. As told in "Jersey Boys," their story is a pretty predictable sequence of rise, fall, (partial) comeback and eventual installation in the Rock and Roll Hall of Fame, but it does embody some saving shades.

That's particularly in the middle, of course, since Tolstoy's comment about unhappy families being unhappy in different ways also applies to singing groups. The seeds of their fall are right there in the particular nature of their rise, especially in the controlling, obsessive character of Tommy DeVito (Christian Hoff).

Still, it's the music that makes us care, and for this, as with pop music in general, it matters whether pre-Beatles 1960s pop (with a brief disco rebirth in the '70s) still reverberates in your emotional memory.

To my surprise, a lot of this does in mine: "Sherry," "Walk Like a Man," "December, 1963 (Oh What a Night)," "Working My Way Back to You" -- they still work, for which we can credit the chops of the main performers, John Lloyd Young as boy wonder Valli, Daniel Reichard as composing genius Bob Gaudio, J. Robert Spencer as lanky Nick Massi and Hoff -- in addition to a small, dynamite on-stage band, with drummer Kevin Dow in propulsive central place.

One qualm: Is the music really live? Hard to tell. Some piano sequences are mimed, so what about the rest? (See how suspicion creeps in as technology proliferates?)

At the August Wilson Theatre (the first time we've used that new name this way), 245 W. 52 St.; call 1-800-432-7250.

'Light in the Piazza'

Now for something finer far. Craig Lucas' script, based on the novel by Elizabeth Spencer, takes us to a somewhat idealized version of 1953 Italy, when Americans were still the saviors of World War II and the dollar was riding very high. In concert with Guettel's music, sensitive direction by Bartlett Sher and deft and lovely sets, costumes and lights (Catherine Zuber, Michael Yeargan, Christopher Akerlind), the story shimmers with a tantalizing atmosphere of yearning love and nostalgic regret.

That's the effect. The story is rather like an early Henry James comedy. Returning to a place she was once happy is Margaret Johnson, a southerner of some means, bringing her beautiful daughter, Clara. We soon learn that Clara is "special," in the modern sense, supposedly stuck mentally and perhaps psychologically in early adolescence, even though chronologically she's in her late 20s and visually she's a pristine 21.

How to explain this to the nice Italians they meet? -- especially to the young man who falls for Clara hard, bringing the Johnsons into his tempestuous family circle (a little caricature, here).

And Margaret's dilemma is the kernel that really makes "Light in the Piazza" work. Margaret faces an intense moral/parental dilemma that commands our concern. Perhaps Clara has grown. Risk, after all, is everything.

Margaret may not solve her challenge as we would -- or at least as we would wish, real life being so much more troubling than fiction. Indeed, Lucas and Co. may indulge us all in a little wish fulfillment in what Margaret does or does not do, but the dilemma remains, preying on our minds and hearts.

Meanwhile, Guettel ravishes us with his handsome music, not a series of anthems or ballads, not even especially rich in memorable melody, but insinuating and compelling nonetheless. It's the kind of score you want to savor by CD, especially given the mental images the show provides to accompany your reverie.

Victoria Clark, a favorite with me for her recent "Bells Are Ringing" and "Guys and Dolls" at Pittsburgh CLO, has reaped deserved praise as well as a Tony for playing Margaret with a feeling delicacy that is also comic and spunky. Kelli O'Hara shimmers as Clara and hints as much at her limitations as the creative team will allow: After all, this is a feel good romance.

The quality of the support is evident in the old performing friends who make up the comic opera Naccarelli family of the young lover played by Aaron Lazar: Charis Sarandon, Michael Beresse, Sarah Uriarte Berry and Patti Cohenour.

How lovely once again to see the language of cigarettes. It's a charmer all around.

At Lincoln Center's Vivian Beaumont Theatre, 150 W. 65 St., through March; call 1-800-432-7250.